1. Field of the Invention
This invention relates broadly to well drilling, more particularly to drilling muds used in oil and gas well drilling, and, especially water based drilling mud additives.
2. Prior Art
In the course of drilling oil and gas wells and the like by means of a rotary well drilling apparatus, circulation fluid or drilling mud is pumped down through a rotary drill pipe and discharged at or adjacent the bit at the lower end thereof. In normal drilling operations, a portion of this circulation fluid returns upward through the well bore and is conducted to a sump where it is filtered and returned to the pump and, again, pumped down the drill pipe.
The primary functions of the circulation fluid or drilling mud are: (1) to lubricate and cool the drilling bit; (2) to suspend the cuttings from the drilling operations so that they are carried to the surface and removed; (3) to prevent excessive amounts of fluids from flowing from the hole into surrounding formations by depositing on the wall of the hole a thin, but substantial, impervious filter cake; (4) to serve as a weighting material exerting sufficient pressure to counterbalance any pressure exerted by water, gas, oil, or other earth fluid; and (5) to prevent caving or other intrusions into the drill hole.
Thus, an efficient drilling mud must exhibit numerous characteristics, including, for example, viscosity, initial and 10-minute gel strength, thixotropy, fluid loss prevention, stability under various temperature and pressure operating conditions, stability against contaminating fluids, such as salt water, calcium sulfate, cement and potassium contaminated fluids, etc.
To achieve a drilling mud exhibiting the above characteristics and properties, extensive research has been conducted, resulting in a multitude of drilling muds having a variety of additives to help a particular problem. A more detailed discussion of various proposed solutions to these problems can be seen in the following patents:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 2,579,453 Earl E. Post, et al 12/25/51 2,634,098 Arthur L. Armentrout 4/07/53 2,667,224 G. C. Howard 1/26/54 2,773,670 George Miller 12/11/56 2,812,161 Eldon J. Mayhew 11/05/57 2,935,473 E. G. King, et al 5/03/60 3,006,846 Charles A. Stratton 10/31/61 3,020,232 Joseph Bayne Doughty 2/06/62 3,034,982 K. P. Monroe 5/15/62 3,070,165 Charles A. Stratton 12/25/62 3,089,842 Charles A. Stratton 5/14/63 3,095,392 F. W. Herrick 6/25/63 3,135,727 K. P. Monroe 6/02/64 3,200,070 F. W. Herrick 8/10/65 3,244,623 Ellis Gray King, et al 4/05/66 3,280,912 J. R. Sheffield, Jr. 10/25/66 3,322,668 Ison G. Fontenot, et al 5/30/67 3,388,061 Aaron E. Markham 6/11/68 3,686,119 Aaron E. Markham, et al 8/22/72 3,700,728 Speros E. Moschopedis, et al 10/24/72 ______________________________________
However, none of the present day drilling muds provide at both high and low temperatures, as well as a broad spectrum of actual drilling conditions, the desired degree of function performance needed by the industry.